Commercially raised pigs are sensitive to a wide spectrum of intestinal diseases or syndromes that are collectively referred to as porcine proliferative enteropathy (PPE). These diseases include intestinal adenomatosis complex (Barker I. K. et al., 1985, In “Pathology of Domestic Animals,” 3rd Edition, Vol. 2 p. 1-237, eds. K. V. F. Jubb et al. (Academic Press: Orlando)), porcine intestinal adenomatosis (PIA), necrotic enteritis (Rowland A. C. et al., 1976, Veterinary Record 97:—178-180), proliferative haemorrhagic enteropathy (Love, R. J. et al., 1977, Veterinary Record 100: 473), regional ileitis (Jonsson, L. et al., 1976, Acta Veterinaria Scandinavica 17: 223-232), haemorrhagic bowel syndrome (O'Neil, I. P. A., 1970, Veterinary Record 87:742-747), porcine proliferative enteritis and Campylobacter spp—induced enteritis (Straw, B. E., 1990, Journal of American Veterinary Medical Association 197: 355-357).
One major type of PPE is non-haemorrhagic and is manifested by porcine intestinal adenomatosis (PIA). This form of PPE frequently causes growth retardation and mild diarrhea. Another important type of PPE is haemorrhagic. It is often fatal, and is manifested by proliferative haemorrhagic enteropathy (PHE) wherein the distal small intestine lumen becomes engorged with blood.
While PPE in pigs is commercially most important, PPE is also a problem in the raising of hamsters (Stills, H. F., 1991, Infection and Immunology 59: 3227-3236), ferrets (Fox et al., 1989, Veterinary Pathology 26: 515-517), guinea pigs (Elwell et al., 1981, Veterinary Pathology 18: 136-139), rabbits (Schodeb et al., 1990, Veterinary Pathology 27: 73-80) and certain birds (Mason et al, 1998).
The organism that causes PPE is the Campylobacter-like bacterium “L. intracellularis” (McOrist S et al, 1995, International Journal Of Systematic Bacteriology 45: 820-825). This organism is also known as lleal symbiont intracellularis (Stills, 1991, supra). PPE-like diseases in pigs may also be caused by other species of Campylobacter (Gebhart et al., 1983, American Journal of Veterinary Research 44: 361-367).
L. intracellularis is located in the cytoplasm of villi and intestinal crypt cells of infected animals, where it causes structural irregularities and enterocyte proliferation. Abscesses form as the villi and intestinal crypts become branched and fill with inflammatory cells.
Current control of PPE relies on the use of antibacterial compounds. There is, however, a need for alternative means of controlling L. intracellularis infection.
International Patent Application No. PCT/AU96/00767 describes L. intracellularis polypeptides and immunogenic compositions that are useful as vaccines. There is, however, a need for additional compositions that confer resistance to L. intracellularis infection.